How Earth Materials Dissolve One way that calcite dissolves in water CaCO3 + H2CO3 → Ca2 + Calcite + Carbonic acid 2 (HCO3 ) − Calcium + Bicarbonate ion ion in solution 15.02.b ©2019 McGraw-Hill Education. How Rock Oxidize Near Earth’s Surface and How the Process of Hydrolysis Operates (don’t copy this formula down – it’s in the book) 4FeSiO3 + O2 → 2Fe2O3 + 4SiO2 pyroxene oxygen hematite silica Oxidized (in water ) Not oxidized K-feldspar + water kaolinite (clay) + potassium (in water) + silica (in water) 15.02.c,d ©2019 McGraw-Hill Education. Rock dissolved and parts converted to red clay How Weathering Makes the Oceans Salty 15.02.e1 ©2019 McGraw-Hill Education. Controls on How Minerals Weather Chemical Bonding Quartz (strong bonds) much less soluble Calcite (weak bonds) soluble; dissolves Response to Weathering Limestone is calcite (soluble) ©2019 McGraw-Hill Education. Most sandstone is Different minerals less soluble quartz weather differently 15.03.a Observe what happens when granite weathers ©2019 McGraw-Hill Education. 15.03.b Factors that Influence Weathering 15.03.c1 ©2019 McGraw-Hill Education. Role of Climate in Weathering Climate reflects temperature, precipitation, and seasonality, so influences weathering, plants, soil, etc. ©2019 McGraw-Hill Education. 15.04.a1 How Slope Influences Weathering 15.04.b1 ©2019 McGraw-Hill Education. Life and Time Influence Weathering Biological activity causes weathering, such as root breaking apart rocks and plant-derived acids attacking materials in soil Time is crucial factor in weathering. More time = more weathering 15.04.c,d ©2019 McGraw-Hill Education. Observe how weathering produces rounded features Many rocks have sharp angular edges Edges and corners begin to smooth Weathering rind No sharp edges or angular features Spheroidal weathering 15.05.a,b ©2019 McGraw-Hill Education. How Do Caves Form? 15.06.a1 ©2019 McGraw-Hill Education. What Features Accompany Caves? 15.06.c1 ©2019 McGraw-Hill Education. Karst Topography Karst topography: produced by weathering and erosion of soluble rocks Pinnacles and dissolved rocks 15.07.a ©2019 McGraw-Hill Education. Spatial Distribution of Karst in U.S. 12.07.b2 ©2019 McGraw-Hill Education. Observe this cut through a soil Soil layers are horizons and assigned letters Not all soil horizons are present in every soil: depends on climate and whether top eroded away 15.08.a ©2019 McGraw-Hill Education. Processes of Soil Formation Where Material Comes From How Material Moves 15.08.b1 ©2019 McGraw-Hill Education. Observe soils in tropical climates Extremely leached soil: laterite 15.08.c ©2019 McGraw-Hill Education. Observe soils in temperate climates 15.08.c ©2019 McGraw-Hill Education. Observe soils in arid climates 15.08.c ©2019 McGraw-Hill Education. Activities that Threaten Soil Overgrazing 15.09.b Removing vegetation ©2019 McGraw-Hill Education. Erosion Soil contamination Observe some problems related to soil Liquefaction Liquefaction during an earthquake Swelling clays Soil compaction Road destroyed by swelling clays Cracks caused by compaction 15.09.c ©2019 McGraw-Hill Education. Role of Gravity in Slope Stability Gravity acts vertically so block will not move on a flat surface Gravity pulls block at an angle so block can move on an angled slope 15.10.a1 ©2019 McGraw-Hill Education. Consider how steep a slope can be and remain stable 15.10.b ©2019 McGraw-Hill Education. Factors that Control Slope Stability Amount of water Angle of repose for material Discontinuities: fractures, cleavage and bedding 15.10.c ©2019 McGraw-Hill Education. Observe some events that could trigger slope failure 15.10.d1 ©2019 McGraw-Hill Education. Observe some ways that slopes fail Earthquake activity Undercut cliff Undercut slope Too steep a slope Landslide ©2019 McGraw-Hill Education. 15.11.a Classification of Slope Failures Mechanism of Movement Fall Flow Solid rock Unconsolidated Fast Slow Type of Material Rate of Movement ©2019 McGraw-Hill Education. 15.11.b What happens when rock or debris falls? Rock fall or debris fall 15.12.a ©2019 McGraw-Hill Education. What happens when rocks slide? Rock slide Rotational slide (or slump) 15.12.a ©2019 McGraw-Hill Education. Geometry of a Rock Slide 15.12.b1 ©2019 McGraw-Hill Education. Viaont Disaster, Italy Wave overtopped dam, flooded downstream towns 15.12.t1 ©2019 McGraw-Hill Education. Observe slope failures that involve flow or weak materials Creep Debris slide Earth flow 15.13.a ©2019 McGraw-Hill Education. Observe the types of slope failure that involve flow: Part 2 Debris flow Rock or debris avalanche 15.13.a ©2019 McGraw-Hill Education. Slope Failures in the U.S. Earth flow – New York Debris avalanche – Alaska Rock slide – Wyoming ©2019 McGraw-Hill Education. Landslide – Utah 15.14.a Landslides and La Conchita 15.14.t1 ©2019 McGraw-Hill Education. Observe the potential for landslides in the U.S. Red = high potential Yellow/green = intermediate Unshaded = low or unknown 15.14.b1 ©2019 McGraw-Hill Education. Recognizing Prehistoric Slope Failures Hummocky topography Broken, angular rocks ©2019 McGraw-Hill Education. Prehistoric deposits Rock types that do not belong 15.15.b Assessing Potential for Slope Failure Past failures Changes in slope Known problems Conditions of material Steep slopes Potential triggers 15.15.c ©2019 McGraw-Hill Education. Setting of Slumgullion Landslide, CO Able to move down a gentle slope (7-10°) in part due to abundant water 15.16.a1 ©2019 McGraw-Hill Education. Slows in winter when some water freezes Studies of Landslide USGS mapped different parts Studied soils of parts: better developed soil on older parts 15.16.a-c ©2019 McGraw-Hill Education. Investigation: Which Areas Have Highest Risk of Slope Failure? 15.17.a1 ©2019 McGraw-Hill Education. Investigation 15.17.a1 ©2019 McGraw-Hill Education. Chapter 16 Streams and Flooding ©2019 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Yukon Delta Bering Sea Observe features on this satellite image that may be related to a river 16.00.a1 ©2019 McGraw-Hill Education. Yukon Drainage Area 16.00.a2 ©2019 McGraw-Hill Education. Drainage Basins Observe the red and blue areas and their boundary Red area drained by one stream, and blue area by another: each is a drainage basin 16.01.b1 ©2019 McGraw-Hill Education. Volume of Flow Versus Time Plot of discharge versus time is a hydrograph This hydrograph shows discharge (flow) increasing during a flood, then decreasing as flood ends Runoff from steep drainage basin is fast and most water arrives downstream at once Runoff from basin with gentle slopes is spread out over time; less peak flow 16.01.a,b ©2019 McGraw-Hill Education. Discharge Versus Basin Shape 16.01.b ©2019 McGraw-Hill Education. Tributaries and Drainage Networks Types of Drainage Patterns Dendritic ©2019 McGraw-Hill Education. Radial Structurally controlled 16.01.c-d North American Drainage Basins Observe these drainage basins and find where runoff in your area ends up 16.01.d4 ©2019 McGraw-Hill Education. How is Material Transported and Deposited? 16.02.a1 ©2019 McGraw-Hill Education. What Processes Erode Material? 16.02.b1 ©2019 McGraw-Hill Education. Turbulence 16.02.c1 ©2019 McGraw-Hill Education. Observe how stream gradient changes downstream Gradient = change in elevation for a horizontal distance (small blue triangles) Usually expressed as m/km or ft/mile Steeper gradient: stream drops more for a given distance ©2019 McGraw-Hill Education. 16.03.a1 How Does a Stream Change Downstream? T1-T3 = tributaries H = headwaters D = delta M = mouth 16.03.a ©2019 McGraw-Hill Education. Sediment Size Versus Current Velocity Observe and interpret this graph of stream velocity versus mode of transport for different sizes of sediment 16.03.b1 ©2019 McGraw-Hill Education. How Do Streams Vary Over Time? Streams vary in discharge during the year due to snowmelt, wet/dry seasons, etc. Suggest some factors that might explain this pattern above (many possible answers) 16.03.c1 ©2019 McGraw-Hill Education. How Do Streams Change Downstream? Observe this vertically exaggerated profile of a river and describe this pattern 16.04.a2 ©2019 McGraw-Hill Education. Base Level The lowest level to which a stream can erode: base level 16.04.b1 ©2019 McGraw-Hill Education. Curves in Streams 1 Observe the channels in three streams Braided: network Low sinuosity: of interweaving gently curved channels ©2019 McGraw-Hill Education. Meandering: very curved; high sinuosity 16.05.a Curves in Streams 2 Observe these satellite images of streams This stream is braided This stream has meanders 16.05.a ©2019 McGraw-Hill Education. What Processes Operate on Meanders? Small graphs show profiles across the stream channel; observe the channel profiles for different parts of the stream Erosion and deposition may be balanced 16.05.b1 ©2019 McGraw-Hill Education. How Do Meanders Form and Move? 16.05.c ©2019 McGraw-Hill Education. Landforms in the Headwaters of Streams 16.06.a3 ©2019 McGraw-Hill Education. Observe this view of a braided stream 16.07.a1 ©2019 McGraw-Hill Education. Close-Up Views of Braided Stream 16.07.a ©2019 McGraw-Hill Education. Observe the features of a low-gradient stream Terraces along some streams 16.08.a1 ©2019 McGraw-Hill Education. Observe this stretch of the Mississippi River for features typical of low-gradient streams 16.08.a6 ©2019 McGraw-Hill Education. How Do Levees Form? 16.08.a ©2019 McGraw-Hill Education. Mississippi River Delta 16.09.a1 ©2019 McGraw-Hill Education. Sediment Deposition in a Delta 16.09.a3 ©2019 McGraw-Hill Education. When a Stream Approaches Base Level Nile River spreads out and deposits sediment (delta) 16.09.a-b ©2019 McGraw-Hill Education. Lena River splits into distributary system What do you think are the consequences of a dam? New temporary base level 16.09.c1 ©2019 McGraw-Hill Education. Lower Mississippi River Gray: recent sediment Yellow/orange: older seds. Other colors: older rocks River above older trough 16.10.a ©2019 McGraw-Hill Education. Upper Mississippi River Before 15,000 years ago, ice covered region (river did not exist) Ice sheets melted and formed upper part of river 16.10.a ©2019 McGraw-Hill Education. What is the Fall Line? Fall Line: waterfalls at boundary of hard and soft rock 16.10.a5 ©2019 McGraw-Hill Education. What Conditions Change Streams? Uplifted mountains increase sediment 16.10.b ©2019 McGraw-Hill Education. How Does Climate Affect Streams? Early streams flowing on broad valleys Climate caused streams to incise,

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